We denote two of our SELD systems that ranked second in the team categories of the 2020 and 2021 DCASE challenges as NTU'20 and NTU'21, respectively. Table REF  shows the performances of the baselines, the top-ranked solutions, and our second-ranked systems in 2020 and 2021. NTU'20 is an ensemble of sequence matching networks [1]}, [2]} while NTU'21 is an ensemble of different models trained on our new proposed SALSA features for SELD [3]}. Both systems use the class-wise output format, which can only detect a maximum of one event of a particular class at a time. Both systems outperformed the respective baselines by a large margin, and only perform slightly worse than the respective top-ranked system. The 2020 results in Table REF  were computed using the 2020 SELD evaluation metrics. For subsequent sections, the results of the NTU'20 system were recomputed using the 2021 metrics.
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